Plottable.js is a library for easily creating flexible, interactive, and performant charts for the web. It is built on top of D3 and provides higher-level pieces, like plots, gridlines, and axes. As such, it's easier to quickly build charts.

Cytoscape.js is an open-source graph library written in JavaScript. You can use Cytoscape.js for graph analysis and visualisation. It's compatible with CommonJS/Node.js, jQuery 1.4+, and plain JavaScript.

JointJS is a modern HTML 5 JavaScript library for visualization and interaction with diagrams and graphs. It can be used to create either static diagrams or, and more importantly, fully interactive diagramming tools and application builders. JointJS makes it easy to create visual languages & tools of various kinds.

The event-driven nature together with MVC architecture of JointJS makes it easy to plug-in any backend application.